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Found 128 results

1. ## How to rotate a gaz resize dynamic node inside a flip fluids dop node

Hi, I'm struggling with an issue I have at the moment where I have a boat that floats along an ocean surface which follows a curve. The idea is to have a path and an ocean I can evaluate and have a boat bob to the waves (I've done this part) and have a guided ocean simulation follow along with the boat. I've then taken the normal and the up vector and used trigonometry, one unit length circle and vex to create Y rotational data. Then by diving into the ocean source node and applying this to ocean evaluate and boundaries with out interfioring with the ocean spectrum I end up with a rectangular particle source that rotates with the boat allowing me to have a smaller source of particles (instead of a large square centred on the boat) that highlight the back and side of the water next to the boat. My problem from here is the flip fluid solver only takes the centre and size from the ocean source, held inside gas resize fluid dynamic nodes of the flip solver. This gives my fluid simulation an incorrect result. I'd like to be able to apply the rotational values to the flipsolver using position, object position, motion node or anything else that would work. However upon facing this problem I've realised my knowledge in dops is extremely lacking and I'm confronted with green and purple outputs of nodes that don't like working together. I have a feeling this is possible due gas resize nodes ability to rotate for clustering and other pyro Sims, I just have no idea how. Can post my hip when I'm back from work later today, if you have any questions please ask.
2. ## RBD Sim wont behave as individual objects?

Hi Guys, Very new to houdini so spare the studpidty, Ive set up multiple rocks in sops using the copy to points node. I wish to then perform a rigid body simulation on these rocks so that they collide with both the ground plane and each other. However, the effect im achieving is the group of rocks falling and interacting with the ground plane as a single large grouped entity. This is despite me setting the bullet collision data as concave and not concave. Thanks in advance all! Procedural Rocks.hip
3. ## PACKED RBD Vibrates continuously on the ground

Dear all, The plot : -> Am currently simulating a simple shatter with rbdPacked prims + Constraints Glue + a gorund plane, all into a DOP. (nothing Awesome till here). The Questions : -> But, strangely, the little rbds continue to vibrate once fallen on the ground. It looks like continuous vibrating tiny giggly wiggly inter-collisions. Did any body ever had this ? Would it be possible, i've to FORCE STOP them using a desactivating VEX snippet in a DOP/geomety wrangle node ? If anybody had this one time, let me know, please. You will be welcome and it will be pleasure to discuss that point you. Thank you all a lot, cheers.
4. ## vellum Keep uv on deformed mesh by points

Hello ! I hope that you all are ok ! I have a problem that I do not understand ! I made a point simulation from a geometry so that it deforms with an elastic effect. I want the final result to keep the uv's basic geometry. I have the VDB, it does not work well. The deform point works almost perfectly, indeed after a certain moment of the simulation, it pushes certain point anyhow and the geometry is badly deformed. I would like to know how to properly adjust the deform point, or another technique to perfectly keep uv if needed ! Thank you ! at_vellum_sticky_uv_OD.hiplc
5. ## Drop of water simulation flip

Hi!! I'm trying to Drop of water Fx ・Reference movie https://vimeo.com/14054601 https://forums.odforce.net/topic/30773-water-drop-splash/?tab=comments#comment-171664 The conditions I want to do 1.Water droplets are small like sweat 2.I want to make a series of fall and bounce 3.I want to shape like a crown The data I was making is this, but bounce does not work well can you help someone drop_190419.hipnc
6. ## SOP Solver and DOP import help

Hello all! I have a question concerning SOP Solvers in an Auto DOP Network. Im using SOP Solvers and switches to activate fracture geometry at certain times. I am trying to activate a second RBD object in the scene. Inside my SOP solver how do I specify which object the DOP import node fetches from the network? My_Scene.hipnc
7. ## Glue bullet

Hello good people! Freshly new in Houdini and I am trying to tackle the basics here. I am trying to break apart a box using voronoi fracture (works) and the add a glue constraint relationship in the dop network (I have failed here utterly). I have spent about two days trying out just about everything I can find or think of and to no avail. I am using an attribute wrangle to add a constraint name to the connected pieces. My constraint network however tells me that the required data is not found or is the wrong type. I am using bullet as my rigid body solver and I have hit a complete brick wall - I just can not get it to work. I am attaching the .hip file, and I would be immensely grateful if someone could help me understand what I am doing wrong. It seems so simple yet I am completely stuck with this issue. Glue issue.hip
8. ## Duplicate objects in RBD pop net

DOP net question. I want to start with a set number of boxes and have them move around with POP forces and bounce off each other with RBD. Problem is that I end up with two items for each one I put in. For the POP source I setup Impulse activation to be \$F == 2. If I use 1 there, I only get one set of items but they aren't effected by the POPAdvect forces. Feels like a rookie mistaken, but I not sure how to set it up. Any ideas? POP Source: Emission Type is All Geo, Geo Source is First Con text RBD Vector Field.hipnc
9. ## Stamping Rest Positions for FEM Objects

Dear Friends, I'm emitting FEM objects into a simulation. Since on a given frame I generate at most one object, I don't need stamping to produce variations, it is enough to animate the initial state. My problem is that these objects share the same rest position, which I would like to vary instead. Is there a way to stamp a variable based on the DOP object currently copying the rest positions to the simulation geometry? In other words is there a function that gives a stable but varying value across objects when a DOP simulation reaches out for rest geometry? Thanks in advance! BMT
10. ## Custom attract

Hi I am trying to create a custom attraction tool using popvops. Its a method I learnt doing a houdini course I would like to improve on it but I have been stuck on it forever. Instead of using a pop attract we are using a popvop to calculate the distance of the particles to a point in space and making them move to this point, if I am using a single point to attract them to its working fine, but what I would like to do is to attract them to multiple points ie a mesh. I have tried using the importpoints but that just makes them go to origin. I would like them to move to the rubber toy. Any advice would be appreciated. I have attached the file and the particle stream I am using to test. Cheers Particles.72.bgeo.sc attraction test.hiplc
11. ## How to reload .sim files

Hi, I am doing a smoke sim. The sim is too large and so I can't simulate the entire sim in one go. I had checked the checkpoint option and gave a valid path to save the checkpoints files then simed half of the simulation and had closed houdini. I want to sim the rest of the simulation but where do I put the .sim files that are generated by the checkpoint so that the sim runs from a certain frame and not from frame 1 all over again?
12. ## Visualise DOP forces

Hello ! Is there a way to visualize the forces in a DOP simulation, much like this, but for wires ? I have a Wind Force (not the pop one), and there is no option to visualize it out of the box. There might be a way to grab the force field information at any location (locations would be a grid of points built specifically for that) and pass it down onto the points to visualize the force on the Normals or smth, but I don't know how to. Something like grabbing the result of all the forces at a location, or only a specific force, either one would be wonderful. Thanks !
13. ## Can I simulate a simplified mesh and then transfer simulation results to original geometry?

Hi, I have an imported geometry which I'd like to use in DOP simulation. Can I simulate a simplified(smoothed) mesh and then transfer simulation results to un-simplified geometry?
14. ## Spring Constraint

Error - Glue constraint references unknown object Would really mean a lot if someone could take a few minutes to look at this file. I was trying to recreate richardlord's spring constraint thingy, but had trouble even beginning to get it to work in the first place. I think there's some changes in constraints from 15-16 (im working in 16). I should have the name attribute matched up to all my constraints and all my objects as the same, but for some reason I get an error with, 'unknown object'. I thought it may have been that the constraint was looking for @rest? Not sure. Very new to creating attributes that get used in dops, I appreciate any insight. springConstraint.hipnc
15. ## Source RBD objects

How is it possible to source in RBD objects (hero) into DOP over time?
16. ## Storing data structuces across time steps in DOPs

Hi everyone Is it possible to store a sparse_matrix data structure across multiple time steps without reforming it at every time step ? I am writing a custom dop solver, so I would like to store it as subdata but I am not quite sure how to do it so any help would be greatly appreciated. I have not really been able to find any examples of this in the documentation ...
17. ## DOP in for-each loop

Hi community! I have a huge destruction scene, where I'm stuck with the ground impact dust. Basically i need to make a smoke sim on every collision with the ground. I have my impact points in place, with birth frame data as well. My guess was to make a for-each loop with a DOP inside of it for every point. It works, but every frame it recalculates the whole sim until the current frame, which is of course is not good. The scene is so huge and scattered, doing this in 1 sim would take an eternity. How can I do this in a correct way? I`m sorry, but i can not post any of the hip file. Thanks for reading this, also a huge thanks if you answer. Cheers. **edit: im on H16.0
18. ## Create Geo with Wrangle in dopnet

Hello there, Is there any way to create Geo dynamically inside a dopnet? Specifically, i would like to have growing tendrils, and simulate those as they are created using popgrains. I created a popwrangle inside my dopnet, and created new points and primitives through vex. Unfortunately, that breaks the pop solver, as its not solving the newly created particles (However, if I put a force after the popsolver it works). I thought maybe that resetting the id to -1 (as used in a similiar way with the bullet solver) would do the trick, but unfortunately not. Is there any way that I can force the popsolver to recognize those newly created particles? Thanks in advance, Bajt createGeoinPop_v01.hiplc
19. ## Animate local transforms in object level

Hi, It seems that generally when animating objects in scene/object level, you are only able to animate variables globally. I have a scene with a spinning propeller, and this spinning propeller needs to rotate around its own axis, while being placed in a certain spot in the scene. How is this achieved? All transforms in the scene are global space, so if you need to rotate the object 30 degrees on the X axis, the Y axis will not follow the local transforms and the propeller will spin sideways in circles. Followup question: I briefly had a teacher from Lost Boys school of VFX and he showed me how to properly load animation data into a dopnet. Unfortunately I was just starting out with Houdini as he showed me, so I did not catch the method. I gathered that this should not be done in sop-level ('Use deforming geometry'), and rather with motion / 'RBD keyframe active' operators in the dopnet -- how do I load in my animation data, so the velocities are correct with proper interpolation? Thank you,
20. ## Wire solver - rotational constraint

Hey guys ! This problem has been bugging me for some time now, so here I am ! So I've got a wire that needs to have one end keep its position and the other end to follow a geometry's animation. I specify the face and/or the point to follow. I have the "keep position" figured out, and half of the other figured. I currently have the "following" end correctly follow the geometry, but only in position. I need the wire to follow the orientation of the face of the moving geometry. I managed to do it following one of Houdini's example scene, but it's not applicable in my case. Or I could not figure out how to apply it to my case, so this test is provided with the scene below. See this for a quick glance at the problem. Thanks ! wire_rot_constraint.hip
21. ## Using Point Position Dop with packed primitives

I'm trying to use the Point Position dop in a rbd packed object sim. Similarly to what is shown in this video. https://www.youtube.com/watch?v=mDkc2gU31sA but with packed objects. In the tutorial he uses the expression dopoption(\$DOPNET,\$OBJID,"CopyInfo","copynum") in the Point Number field. This doesn't seem work on a packed primitives. I don't think there are values for the CopyInfo or copynum parameter. I have tried using @ptnum as shown in the attached screen. Is there a way to use the Point Position dop with packed primitives? thanks

Hello everybody! I would like to simulate particles on top of pre-animated / pre-simulated (cached) points. So far I only managed to do the "transfer v attribute inside a sop solver" trick. Unfortunately it does not give me the result I imagine. Instead of inheriting only the velocity I would rather like the points to be attracted by the pre-animated points so they tumble around and follow them the animated ones. Basically I am trying to animate some points and then do a simulation on top of it to give it a more natural feel and to be able to art direct the simulation better. I would greatly appreciate if somebody could give me a hint or a solution on how to do that? Thank you! Here is my current progress (particles inherit v): pop_transfer_vel.hiplc
23. ## DOP group exprresion

I'm working on a setup where a couple of polygon curves simulated and breaking apart using a wiresolver and a sopsolver. I've only one wire object and would like to group the wires in that object that are broken so I can apply a force to them. I'm using a group DOP node and in the Group 0 Expression I've this expression prim("..:wireobject1/Geometry", \$OBJ, "broken", 0) == 1 The setup works so far so that when prim 0 "broken" attribute evaluates to 1 all the wires belongs to the group and get the force. So I guess it's the \$OBJ I'm using incorrectly. It evaluates to 0 because the wireobject1 is the only object in the DOP network. So how do I access each primitives primnum in DOP? If it's even possible to group primitives belonging to one object like this? Is there another way to create DOP groups? Would like to have something like a Geometry Wrangle with a create setprimgroup expression. Thanks! / John
24. ## DOP Wire solver - differents width

Hi ! First post here, I'm starting Houdini since a few weeks only... I'm wondering how to set different width (for repulsion) for each wire I've created. I've tried to create a random point attribute to drive the width into the wire object but it doesn't seems to work, I feel missing something. Help needed Thanks RANDOM_WIRES_0.1.hip
25. ## blending smoke color in dop (so it looks right)

Hi, I am trying to figure out a way to mix smokecolors in DOPs without the effect of the velocity "Maximum" setting. Its a bit hard to describe so just check out my file. I have two methods of mixing the colors. One is done in DOPs putting Cd in the velcity volume of a source volume and setting it to Maximum. Because it is set to Maximum (because of the lack of another better working mode), colors tend to blend in a (somewhat expected) weird way. so two voxels, one with color (1,1,0) and the other with (0,0,1) then blend together to something that is (1,1,1). And I'm pretty sure blue and yellow smoke do not mix to white smoke ;-) The other one is done using particles which inherit the emitters color and are advected by the smoke. In a postoperation I transfer the color of the particles back into the volume and because it extrapolates it gives a nice colormix that is more of a blend operation and looks correct but its way more processing intensive (especially with highres volumes and lots of particles). So my question is: can the result of the particle workflow be somehow achived in dops without using particles? PS: I did try to do the coloring in a shader and it worked (its not in the file), but I would still need to create particles and I guess there would be a pretty large hit in rendertime sampling those particles in the volume. Cheers, Ronny colored_smoke_v03.hip
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